This invention relates generally to burner guns for burning hydrocarbon fuels in industrial and utility applications, such as in boilers and heating systems. More particularly, the invention relates to burners of this type in which means must be provided for reducing emissions of pollutants such as oxides of nitrogen.
The inherent dangers of air pollution resulting from the combustion of fossil fuels are now widely recognized, and efforts are continually being made to reduce the emissions of harmful pollutants, both from automobile engines and stationary burners used in power generation and in industry. One group of products of combustion that is particularly harmful is that derived from a combination of nitrogen and oxygen. One of these is nitric oxide (NO), a colorless and relatively harmless gas. However, nitric oxide reacts with free oxygen, even at room temperature, to form nitrogen dioxide (NO.sub.2), a yellow-brown gas which is toxic to both plant and animal life. Other oxides of nitrogen may also be produced as a result of the combustion of fossil fuels, and oxides of nitrogen are often referred to nonspecifically by the formula NOx.
Related to the problems of air pollution in industrial burners is an additional consideration concerning the conservation and efficient utilization of energy sources. In recent years, it has become increasingly important for industrial burners to be able to operate on a variety of fossil fuels, to accommodate the continual variations in the availability and cost of fuel oil and natural gas, for example. Accordingly, it is now highly desirable to provide a fossil fuel burner for power plants or other industrial uses which can be readily adapted for combustion of either oil or gas. In the past, separate oil and gas burners of various designs have been provided at the same location in the boiler. However, there is now a significant need for a burner gun capable of alternating between gaseous and liquid fossil fuel usage. The present invention is directed simultaneously to this need and to the continuing need to provide low emissions of oxides of nitrogen and increased efficiency.